I suppose my input would be that if you are stressed about the used bolts failing on you, replace them with new. Problem solved.
I did not replace mine. Visually, they looked good. Most importantly, they are not torque to yield bolts if you torque them to the manufacturer's recommended torque (37 ft lbf). I believe the bolts are M10 (you would have to check this as I don't have them infront of me). Standard torque for class 8.8 bolt is in the realm of 40ft lbf. Where I work, it is 41±7ft lbf. This seems to agree with the what is listed in the service manual. If you have tightened them to the previously mentioned 59 ft lbs, you are approaching or have crossed the yield strength of that bolt. In this case, I would not reuse them.
In regards to bolt fatigue, this should be taken into consideration when designing the bolted joint. Since these are steering components, I imagine there is a large safety factor designed into this bolted joint. At this point this is speculation, but Toyota engineers would most likely have designed the bolted joint so that the loads on each bolt would not exceed their fatigue limit. If you stay below the fatigue limit, the number of load cycles is "theoretically" infinite. To me, this is further proven by Toyota's engineers chosing NOT to call the bolt out as a must replace part in the service manual as pointed out by other posters.
Hold up. Edit. Looking at the pictures OP posted of his bolts, they are "Class 11T" based on the markings as per the service manual page 130 (SS-1). On the following page, the standard torque for a Class 11T M10 hexagon flange bolt is 72 ft lbf. 64 ft lbf for a hexagon head bolt of the same class and size. Therefore, torquing them to 59 ft lbf would be completely understandable in my opinion so long as you verify your bolt grade.
Leaving the rest of my post unedited because I think there is some value in it.
I did not replace mine. Visually, they looked good. Most importantly, they are not torque to yield bolts if you torque them to the manufacturer's recommended torque (37 ft lbf). I believe the bolts are M10 (you would have to check this as I don't have them infront of me). Standard torque for class 8.8 bolt is in the realm of 40ft lbf. Where I work, it is 41±7ft lbf. This seems to agree with the what is listed in the service manual. If you have tightened them to the previously mentioned 59 ft lbs, you are approaching or have crossed the yield strength of that bolt. In this case, I would not reuse them.
In regards to bolt fatigue, this should be taken into consideration when designing the bolted joint. Since these are steering components, I imagine there is a large safety factor designed into this bolted joint. At this point this is speculation, but Toyota engineers would most likely have designed the bolted joint so that the loads on each bolt would not exceed their fatigue limit. If you stay below the fatigue limit, the number of load cycles is "theoretically" infinite. To me, this is further proven by Toyota's engineers chosing NOT to call the bolt out as a must replace part in the service manual as pointed out by other posters.
Hold up. Edit. Looking at the pictures OP posted of his bolts, they are "Class 11T" based on the markings as per the service manual page 130 (SS-1). On the following page, the standard torque for a Class 11T M10 hexagon flange bolt is 72 ft lbf. 64 ft lbf for a hexagon head bolt of the same class and size. Therefore, torquing them to 59 ft lbf would be completely understandable in my opinion so long as you verify your bolt grade.
Leaving the rest of my post unedited because I think there is some value in it.
Last edited:
